The present invention relates to a communication data processing device of a cable television system and, more particularly, to improvements in a data communication processing function between a central station, an external control unit (ECU) and a subscriber processing unit (SPU) by, for example, using the SPU as an I/O port.
In a cable television system (to be referred to as a CATV system hereinafter), television broadcast signals for 64 channels can be transmitted from a central station through a cable. In the CATV system, a function for bidirectional data communication between the subscriber and the central station is added. The communication content includes program data, program reservation data, charge data, service data and the like. However, it is very difficult to process the above communication data by a single central station. As the number of subscribers increases, the processing load of a microcomputer in the central station is increased, and data processing capacity is decreased. When various communication data are concentrated on a cable of the system, data may be erroneously processed.
On the other hand, in the CATV system, it is proposed to transmit a television broadcast signal of a pay channel, or that for a partial pay channel including a pay program within a given time range. When the television broadcast signal including the pay program is transmitted, many operations are needed such as checking of subscribers reserving the pay program, e.g., by polling, fetching of charge data from the subscriber who watched the pay program, and the like. However, if many such operations are processed by the microcomputer in the central station, this results in a complex program, degradation in data processing efficiency accompanying an increase in the number of subscribers, and an increase in occurrence of data error. An increase in the number of subscribers also causes noise concentration of upstream data in a trunk cable.